MINNEAPOLIS - The state is warning homeowners and businesses in the southeast Minneapolis Como neighborhood of potentially harmful vapors coming into their homes.

The Minnesota Department of Health and the Minnesota Pollution Control Agency sent letters to about 200 homes Wednesday, alerting residents of possible seepage of trichloroethylene, a suspected cancer-causing chemical commonly known as TCE.

"It potentially can lead to increased risk of cancer over long periods of exposure, and exposure to TCE [is] associated with increased risk of birth defects," said Jim Kelly, with the Minnesota Department of Health Environmental Surveillance & Assessment.

The Minnesota Department of Health says the most sensitive health effects are to the immune system and a developing fetus, but say there is an increased risk of kidney cancer, liver cancer and non-Hodgkin's lymphoma.

TCE was used on the former General Mills research facility at 2010 East Hennepin from the late 1940s to the early 1960s to degrease metal parts. About 1,000 gallons were dumped in a soil pit on the site.

The contamination had been monitored for 25 years, and seemed to disappear, until teams took 40 soil samples as a precaution in 2011. General Mills, under the direction of the MPCA pumped and treated groundwater at the site to remove the TCE. However,in September, TCE was confirmed in soil gas samples taken on public rights-of-way in the Como neighborhood, prompting this alert to residents.

"Now we know that yes, even groundwater contamination, even low level can produce vapor contamination underground," said Hans Neve, a Minnesota Pollution Control Agency superfund site manager.

General Mills has agreed to install vapor ventilation systems, which will result in no cost to homeowners. The process will begin November 18th, and researchers are asking for the neighborhood's help, allowing teams access to the homes, going into basements, drilling small holes in the floor and collecting vapors underneath the building sub-slab.

"The systems that will be put in will be identical to radon mitigation systems, and what that will do will create a path of least resistance beneath the basement slab," said Kelly.

Residents and property owners that fall within the dotted area on the map are being asked to sign an access agreement, which allows your home to be sampled.